Introduction

Lipids are biology molecules which not soluble in water but soluble in organic solvent. There are many type of lipids in our body with different functions. Only certain lipids are routinely analyse in Medical Laboratory which related to risk assessment and effectiveness of treatment related to cardiovascular disorder.

Type of Lipids

The following are lipids routinely analysed in Medical Laboratory:

1. Total Cholesterol
2. Triglycerides
3. HDL (High density lipoprotein) Cholesterol and
4. LDL (Low density lipoprotein) Cholesterol.

Cholesterol consume from diet and in addition our body can generate it. Triglyceride is an important energy source from lipid in our body. HDL and LDL Cholesterol are Lipoprotein which lipids bound with specific protein (Apolipoprotein). HDL (High density lipoprotein) has highest density followed by LDL (Low density lipoprotein).

HDL also called ‘Good Cholesterol’ while LDL is ‘Bad Cholesterol’ based on ability to transport Cholesterol for metabolisme.
Diet intake fat-rich cause increase of certain type of lipids in our body and could increases risk of cardiovascular diseases. Elevation of blood Cholesterol level could lead to narrowing blood vessel.

Biochemistry Lipid Metabolisme

Products of lipid digestion are fatty acid and glycerol. Both are transported (in the form of emulsion) into intestine epithelial cell. In the cell, both fatty acid and monoglycerol combined become triglycerides and are incorporated into large aggregates, termed chylomicrons. Later chylomicrons transported to liver and adipose tissue.

Inside liver cells and adipose tissue, chylomicrons will be utilised to produce fatty acid and glycerol which later forms triglycerides. The process of formation triglycerides is called esterification. When energy is required from lipid, triglycerides will be utilised to produce fatty acid and glycerol and transported to cells for oxidation and generate energy. The process of lipid degradation/catabolism is called lipolysis.

Oxidation process of fatty acid is called Beta (?) Oxidation and produce Acetyl CoA. Energy (in the form of ATP) will be generated from Acetyl CoA. If there are adequate energy, Acetyl CoA will undergo lipogenesis to form fatty acid and stored as triglycerides.

Some lipids are synthesized from Acetyl CoA. Cholesterol is synthesized via process of cholesterogenesis from Acetyl CoA. Cholesterol undergoes process of steroidogenesis to form steroid.

Lipid Function

Some biology function of lipids identified as;

1. Cell membrane structure component.

In this case lipids act as membrane barrier for cells and help control flow of substances between cells.

1. Source of energy

Lipids are stored in adipose tissue/fat tissue as source of energy when required once carbohydrate fully utilised

• Hormone and Vitamin

Some lipids are component of hormone structure (progesterone and testosterone) and vitamin (Vitamin A, D, E and K). Hormones help to coordinate communication between cells, while vitamins help coordination of biology processes in our body.

1. Emulsification agent

Relationship between Lipids and Diseases

Determination of blood lipid profile is required to assess health status, which include

• Total Cholesterol
• HDL Cholesterol
• LDL Cholesterol
• Triglycerides

Investigation and assessment to all four (4) parameters are required to get better information on health status

Generally Lipid Profile assessment closely related to risk of cardiovascular diseases. Increase level of Total Cholesterol, LDL Cholesterol, Triglycerides and decrease of HDL Cholesterol associated increase risk of heart attack, stroke and hypertension. Lipid profile results fall within expected range can reduce getting risk of cardiovascular diseases.

Healthy individual should do regular (annually) assessment of Lipid Profile as part of Health Screening Programme. Patients who take medication to lowering lipid level, should do continuous lipid profile assessment to ensure drug dosage is adequate

Patient preparation before blood sampling

Lipid Profile assessment can be done through blood sample. Patient should fast 8-12 hours prior test conducted. 3-5 mL blood from venous transferred to suitable container, then send to Medical Laboratory for lipid profile analysis.

Reference interval

Doctor/Clinician will assess result of every parameter lipid profile and considering risk factor such as smoking, diabetes, family history and other before correct treatment started to reduce heart attack risk.

Reference Interval for every parameter lipid profile are different and affected by gender.

Total Cholesterol

• <5.2 mmol/L: Low risk
• 2 – 6.2 mmol/L: Intermediate risk
• > 6.2 mmol/L: High risk

Triglycerides

• <2.26 mmol/L

HDL Cholesterol

• > 1.45 mmol/L (L)** atau >1.68 mmol/L (P)**: Low risk
• 90-1.45 mmol/L (L) atau 1.15-1.68 mmol/L (P): Intermediate risk
• <0.90 mmol/L (L) atau <1.15 mmol (P): High risk

LDL Cholesterol::

• <2.6 mmol/L: Low risk
• 6 – 4.1 mmol/L: Intermediate risk
• >4.1 mmol/L: High risk
  

(M)** – Male (F)** – Female

References

1. Third Report of the Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III): NIH Publication No. 02-5215; 2002
2. Carl Burtis et al; Tietz Textbook of Clinical Chemistry and Molecular Diagnostics, Fourth Edition (2006), Elsevier Saunders Publisher. Lipids, Lipoproteins, Apolipoproteins and Other Cardiovascular Risk Factors (Chapter 26).